html2canvas in angular 4

Question

I am able to take a screenshot using html2canvas in angular 4 but i need to send the string image to the server side using a http post call

Component

import { Component, OnInit, NgZone } from '@angular/core';
import { Router, ActivatedRoute, Params } from '@angular/router';
import { EventsEmitter } from '../../assets/scripts/services/eventsEmitter';
import { WindowRef } from '../../assets/scripts/services/window';
import { ImagesService } from '../images/images.component.service';
import { DomSanitizer } from '@angular/platform-browser';
import * as html2canvas from "html2canvas";


@Component({
    selector: 'categories',
    templateUrl: 'app/components/view/view.component.html',
    styleUrls: ['app/components/view/view.component.css'],
    providers: [ImagesService]
})
export class ViewComponent {
    
   

    constructor(
        private route: ActivatedRoute,
        private router: Router,
        private imagesService: ImagesService,
        private eventsEmitter: EventsEmitter
        private sanitizer: DomSanitizer,
        private window: WindowRef) {
        this.window.nativeWindow.scrollTo(0, 0);
    }

    ngOnInit() {
    }

    pdfDownload() {
        html2canvas(document.body).then(function (canvas) {
            var imgData = canvas.toDataURL("image/png");
            document.body.appendChild(canvas);
        });
    }


    AddImagesResource(query: any) {
        this.imagesService.addCanvasResource(query)
            .subscribe(response => {
                this.eventsEmitter.broadcast('Success', 'Changes Saved Succesfully');
            },
            error => {
                this.eventsEmitter.broadcast('Error', 'Error Occured');
            });
    }
}

<a data-html2canvas-ignore (click)="pdfDownload()">screenshot</a>

Service that i am calling to do a post

 addCanvasResource(body: Object): Observable<any> {
        let bodyString = JSON.stringify(body);
        let headers = new Headers({ 'Content-Type': 'application/json' });
        let options = new RequestOptions({ headers: headers });

        return this.http.post(this.baseUrl + 'api/v3/images/AddCanvasImage', body, options)
            .map((response: Response) => {
                if (response.status < 200 || response.status >= 300) {
                    throw new Error('This request has failed ' + response.status);
                }
                else {
                    return response;
                }
            });
    }  

I am unable to access AddImagesResource() function in html2canvas

can you please tell me how to achieve the above functionality

Answer 1

pdfDownload() {
    let self = this;//use this variable to access your class members inside then().
    html2canvas(document.body).then(canvas => {
        var imgData = canvas.toDataURL("image/png");
        self.AddImagesResource(imgData);
        document.body.appendChild(canvas);
   });
}

Answer 2

When providing the callback for a promise in Angular, you should use an arrow function, rather than an anonymous function. Arrow functions bind to the current context correctly, so the function you are trying to call will be accessible.

Try this instead:

pdfDownload() {
    html2canvas(document.body).then(canvas => {
        var imgData = canvas.toDataURL("image/png");
        this.AddImagesResource(imgData);
        document.body.appendChild(canvas);
    });
}

Answer 3

Make sure to import the script under the scripts list in angular-cli.json

"scripts": [
"../node_modules/html2canvas/dist/html2canvas.min.js"
]

And in the class as:

import * as html2canvas from "html2canvas"